SUBORDER c PERISSODACTYLA 163 



Family 5. Ohalicotheriidae Gill.^ 



? 0. 3.3. 

 Dentition: • bunolophodont ; premolars less complex than molars, 



superior ones with only one internal and one external cone. Superior molars with 

 '^-shaped ectoloph and two unequally large conical internal cusps. Inferior molars 

 with two y -shaped crescents. M^ without third lobe. Long diastema between cheek 

 and front teeth. Skidl ranging from brachycephalic to dolichocephalic. Auditory 

 bulla present. Orbit open posteriorly. Pelvis elongated (Moropus). Third trochanter 

 prominent or wanting. Fore a,nd hind limbs subequal in length or fore limbs longer 

 than hind limbs. Fore feet teiradactyl, afterwards tridactyl. Distal face of 

 astragalus articulating with the navicular and cuboid, or with the navicular only. 

 Distal ends of metapodials with highly convex dorsal articulation for proximal 

 phalanx, or carnivore-like. Terminal phalanges high, laterally compressed, pointed, 

 and deeply bifid. Tertiary ; Europe and North America. Pliocene of India 

 and China. Pleistocene ; Uganda. 



This family was formerly placed in the order Ancylopoda, in which were 

 also included the Homalodontotheriidae. The latter, however, are now con- 

 sidered referable to the suborder Entelonychia, limited exclusively to South 

 America, and exhibiting merely a similar differentiation of the terminal 

 phalanges, which are clawlike as in the Ohalicotheriidae. This latter family 

 must be referred to the perissodactyls, among which, in the structure of their 

 teeth, they are most closely allied to the Titanotheriidae, while some cranial 

 characters are suggestive of the Equidae. The Chalicotheres are distinguished 

 from all typical perissodactyls by a number of highly characteristic features, 

 among which may be mentioned the curiously carnivore-like humerus, the 

 sharply pointed, claw-like, and cleft terminal phalanges, and the carnivore- 

 like convexo-concavity between the metapodials and the proximal phalanges. 

 By means of the latter modification the second digit of the manus is capable 

 of great dorsal flexion. The carpus, on the other hand, is strongly inter- 

 locking as in the perissodactyls, while the astragalus of the pes sometimes 

 articulates as in the latter, that is, with navicular and cuboid (3Iacrotherium), 

 or with the navicular only (Moropus and Nestoritherium). The remains 

 indicate that the animals varied in size from less than half that of an 

 American tapir to larger than a rhinoceros. In the memoir of Holland and 

 Peterson three subfamilies are proposed as follows : — 



Subfamily 1. Schizotheriinae. 



Manus teiradactyl with vestigial pollex (Schizotherium) ; manus and pes less 

 specialised than in later forms (especially in Eomoropus of North America). 



Schizotherium Gaudry (Limognitherium Gervais). Established on fragments 



of the maxillary with premolars and two anterior molars; metatarsals, meta- 



11 3.3. 

 carpals and phalanges associated. Dentition • Upper molars longer 



t £ O .O . 



^ Abel, 0., Lebensweise von Chalicotlierium. Acta Zoologica (Stockholm), vol. i., 1920. — 

 Barbour, E. H., Moropus. Nebraska Geol. Surv., vol. iii., 1908. — Depiret, C, Arch. Mus. Hist. 

 Nat. Lyon, vol. v., 1892, — Filhol, H., Mammiferes de Sansan. Ann. Sci. Geol., vol. xxi., 1891. — 

 Osborn, H. F., Eomoropus. Bull. Amer. Mus. Nat. Hist., 1913. — Peterson, 0. A., Amer. 

 Naturalist, 1907. — Holhmd, W. J., smd Peterson, 0. ^.,Mera. Carnegie Mus. , vol. iii., No. 2, 1914. 



